The precise metering of materials (e.g., dry solids) is very important in many applications, particularly in the manufacturing processes of the numerous processing industries. Usually when such materials are continuously metered into such processes, they must be precisely controlled at specific feed rates so that the processes function as designed, that product formulation is correct, and that the quality of the end product does not suffer. Many of these applications are automated, and productivity demands that they proceed without human intervention to the greatest extent possible.
On a global basis, a number of different types of feeders are utilized for metering the many thousands of different dry solid materials that are regularly used by manufacturers in their various processes. Such materials can be in the form of granules, powders, flakes, chunks, strands, and can be foodstuffs, plastics, chemicals, pharmaceuticals, ceramics, etc., with each possessing its own individual physical handling characteristics. In general, material is provided to a feeder continuously or periodically from storage supply and the feeder discharges the material at a desired output rate. Different feeders, however, have different capabilities, which depend on the design of the individual feeders and their principles of operation.
Feeding mechanisms, especially when feeding adhesive, cohesive, fibrous, or hygroscopic dry solids materials, sometimes experience problems in handling the material due to the material either sticking to the walls of a supply hopper blocking downward flow, or bridging of the material in the feeding mechanism itself and/or the supply hopper supplying material to the feeder (e.g., compaction due to the adhesive, cohesive and/or compressible nature of the material).